Optical fiber cord

ABSTRACT

A single core optical fiber cord having an outer diameter of 1.2 mm or less, and having a structure in which an optical fiber core wire having a resin coating provided at the center, a tensile-strength-fiber layer around the periphery of the optical fiber core wire, and a coating layer around the outer periphery of the tensile-strength-fiber layer is provided. The coating layer can be composed of a non-halogen fire-retardant resin. The optical fiber cord has excellent fire retardant, mechanical and handling properties, although the outer diameter thereof is 1.2 mm or less.

TECHNICAL FIELD

The present invention relates to an optical fiber cord used for systemlines or the like in a bureau or premises. More specifically, thepresent invention relates to an optical fiber cord that has excellentfire-retardant, handling, mechanical, and transmission properties; thatemits no harmful substances, such as dioxins, during incineration afterbeing removed; and that hardly allows harmful substances, such as heavymetal compounds, to dissolve out in the reclamation process.

BACKGROUND ART

In recent years, as the demand for optical communication network hasincreased, system lines in a bureau or premises are required to containa larger number of core cords therein. In order to allow lines tocontain a larger number of core cords therein, a wide space has to beallocated for lines. However, as the space for lines in a bureau orpremises is limited, making the respective diameters of optical fibercords smaller is essential. It should be noted, however, that when thediameter of each optical fiber cord is made smaller, the optical fibercords still need to be held in a loose state, so that a core wire doesnot buckle when the core wire is pushed into the optical fiber cord atthe time of attaching a connector; and the mechanical properties, suchas the tensile strength and bending rigidity of the optical fiber cord,still need to be kept at a predetermined level or higher, so thatexcellent handling properties are maintained in jumper ring, such asline-switching. In addition, as the optical fiber cords are usedindoors, they must have an excellent fire-retardant property. Due tothis, polyvinyl chloride (PVC) has conventionally been used as a coatingmaterial thereof.

As examples of efforts to make the diameter of optical fiber cordsmaller, there are JP-A-10-10380 (“JP-A” means unexamined publishedJapanese patent application), JP-A-2000-28875, and the like. Theseexamples are characterized in that the diameter of conventional opticalfiber cord is made smaller.

On the other hand, in recent years, there has been a problem that, whena coating material containing polyvinyl chloride or a halogen-seriesfire-retardant agent is discarded without being properly treated, forexample, a plasticizer and/or a heavy metal stabilizer, which have beenblended in the coating material, dissolve out. In addition, anotherproblem, that a large quantity of smoke and hazardous/corrosive gasesare generated when such a coating material is burned, has been an issue.In particular, it has recently been reported that the coating materialmay be a source of dioxin.

In consideration of such an influence on the environment by a coatingmaterial containing PVC or a halogen-series fire-retardant agent,non-halogen fire-retardant coating material, in which metal hydrates arefilled at a high concentration in a polyolefine-series resin component,has been studied, in place of the coating material containing halogens,such as polyvinyl chloride. As one example in which a non-halogenfire-retardant coating material is used for a coating material of anoptical fiber core wire or an optical cord, there are JP-A-9-33770 etc.However, this conventional example is characterized in that it onlyattempts to make the conventional optical fiber cord fire-retardant by anon-halogen material, and it gave no consideration to other matters,including making the diameter of the optical fiber cord smaller.

When an optical fiber cord is coated with a composition in which metalhydroxides are filled at a high concentration, if the diameter of theoptical fiber cord is made smaller, a base resin having relatively lowelastic modulus must be used as the base resin of the coating material,so that the fire-retardant agent is blended at a high concentration andin an excellently dispersed manner. Accordingly, it has been difficultto obtain mechanical properties, such as bending rigidity, that arenecessary for an optical fiber cord. In particular, in the case of theouter diameter of the optical fiber cord is 1.2 mm or less, when asingle layer of a composition in which metal hydroxide is filled at ahigh concentration is used as the coating of the optical fiber cord,bending rigidity of a given level necessary for the optical fiber cordmay not be obtained, or a problem that, when the optical fiber cord isheld for a long time so as to have a constant bending diameter, theoptical fiber cord tends to remain in a bent form even after the cord isreleased, may arise. Further, when jumper ring (switching of opticallines) of optical fiber cords is performed, an operation for pulling outdesired optical fiber cord terminals from a bundle of densely linedoptical fiber cords is necessitated. In order to avoid the occurrence ofbuckling of the cords during the operation, bending rigidity of acertain value or higher is necessary.

The present invention has been contrived to solve the aforementionedproblems. An object of the present invention is to provide an opticalfiber cord having a diameter that has been made smaller, to 1.2 mm orless, and having excellent fire-retardant, mechanical, and handlingproperties.

Other and further objects, features, and advantages of the inventionwill appear more fully from the following description, taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a sectional structural view showing one example of an opticalfiber cord.

FIG. 2 is an explanatory view showing an evaluation method of bendingrigidity of the optical fiber cord.

FIG. 3 is an explanatory view of showing a method of 90° bending test ofan optical fiber cord having a connector.

DISCLOSURE OF THE INVENTION

The aforementioned objects of the present invention can be achieved bythe following invention.

Namely, the present invention provides:

-   -   (1) An optical fiber cord which is a single core optical fiber        cord having an outer diameter of 1.2 mm or less, and has a        structure in which an optical fiber core wire having a resin        coating is provided at the center, a tensile-strength-fiber        layer is provided around the outer periphery of the optical        fiber core wire, and a coating layer is further provided around        the outer periphery of the tensile-strength-fiber layer, wherein        the coating layer is composed of a non-halogen fire-retardant        resin;    -   (2) The optical fiber cord as stated in the above item (1),        wherein the coating layer is formed by a composition in which        18-60 parts by mass of ammonium polyphosphate is blended with        100 parts by mass of a resin component containing at least one        selected from the group consisting of polyamide-series        thermoplastic resins, polyamide elastomer-series thermoplastic        resins and polyester elastomer-series thermoplastic resins;    -   (3) The optical fiber cord as stated in the above item (2),        wherein the ammonium polyphosphate is one that has been        surface-treated;    -   (4) The optical fiber cord as stated in the above item (1),        wherein the coating layer is formed by a composition in which        18-60 parts by mass of a fire retardant, which consists of        ammonium polyphosphate and a nitrogen-containing compound, is        blended with 100 parts by mass of a resin component containing        at least one selected from the group consisting of        polyamide-series thermoplastic resins, polyamide        elastomer-series thermoplastic resins and polyester        elastomer-series thermoplastic resins;    -   (5) The optical fiber cord as stated in the above item (4),        wherein the ratio of said ammonium polyphosphate to the total        amount of said ammonium polyphosphate and said        nitrogen-containing compound is 50 mass % or more;    -   (6) The optical fiber cord as stated in the above item (5),        wherein said ammonium polyphosphate is one that has been        surface-treated.

According to the present invention having the aforementioned structure,an optical fiber cord having excellent fire retardant, mechanical,transmission and handling properties can be provided when the diameterof the optical fiber core wire or the optical cords is made smaller.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferable embodiment of an optical fiber cord according to thepresent invention will be described with reference to drawings.

FIG. 1 is a sectional view of an optical fiber cord according to thepresent invention. In the drawing, 1 represents an optical fiber cord, 2represents an optical fiber core wire, 3 represents a tensile strengthfiber layer and 4 represents a coating layer as an outer coating.

The optical fiber core wire used in the present invention means anelemental wire which is an optical fiber itself, or it means an opticalfiber core wire that has been subjected to a surface treatment, such asresin coating, thereon.

The optical fiber core wire having a resin coating thereon used in thepresent invention preferably has the outer diameter of 0.25-0.70 mm, andmore preferably has the outer diameter of 0.4-0.6 mm. When the outerdiameter is too small, the transmission loss caused by the bending ofthe optical fiber cord increases and the side pressure propertysignificantly deteriorates. On the other hand, when the outer diameterof the optical fiber core wire is too large, it becomes difficult toachieve a loose structure with keeping the outer diameter of the opticalfiber cord outer 1.2 mm or less. If the loose structure is notmaintained, there is a possibility that buckling of the core wire occursat the time of attaching a connector. Here, the “loose structure” meansa state in which the core wire in the optical fiber cord does notclosely attach to a tensile strength fiber or an outer coating providedaround the outer periphery thereof, except that the core wire attachesto a tensile strength fiber or an outer coating due to frictionalcontact therebetween, and at the time of attaching a connector, theoptical fiber cord wire is pushed into the inside of the optical cord,without buckling, so as to be accommodated in the optical cord with aredundant portion thereof. In this case, if the amount of the tensilestrength fiber is reduced in order to maintain the loose structure, therequired tensile property may not be obtained. Therefore, it isgenerally preferable the maximum outer diameter of the core wire is 0.7mm.

In addition, as the tensile strength fiber of the present invention, thearamid fiber (trade neme: Kevlar, Twaron and the like) and the PBO(polyparaphenylene benzobisoxazol) fiber (trade name: ZYLON) arepreferably employed. In order to achieve the tensile property requiredfor the optical fiber cord and the outer diameter dimension of theoptical fiber cord of 1.2 mm or less, the tensile elastic modulus of thetensile strength fiber is preferably in the range of 70,000 to 120,000MPa. Further, in order to evenly arrange the tensile strength fiberaround the outer periphery of the core wire, the total amount of thetensile strength fiber in a state in which a plurality of fiber bundlesthereof are provided around the core wire is preferably 100-220 mg/m(1000-2200 decitex). Among these tensile strength fibers, the PBO fiberhas more than twice as much elasticity modulus as that of the aramidfiber and thus allows more freedom in designing the structure of theoptical fiber cord.

In the present invention, the tensile strength fiber layer is providedaround the outer periphery of the optical fiber core wire, as shown inFIG. 1. The tensile strength fiber layer is located between the opticalfiber core wire at the center and the outer coating resin layer, is notbrought into contact with the optical fiber core wire and the outercoating resin layer except that such a contact occurs due to thefrictional contact between their surfaces, and is provided around theperiphery of the optical fiber core wire in an un-intertwined(longitudinally attached) or intertwined manner. The area occupancy rateof the tensile strength fiber layer in the section of the optical fibercord is not particularly limited, but preferably 10-70%, and morepreferably 30-50%.

In the present invention, a thermoplastic resin which constitutes theouter periphery of the optical fiber core wire and the tensile strengthfiber may be designed as a single layer or more than one layers.However, as the outer diameter of the optical fiber cord is to be 1.2 mmor less, the thickness of the coating layer as the outer coating ispreferably 0.10-0.30 mm. In addition, the bending modulus of the baseresin component of the coating material is preferably 500-1,300 MPa, interms of the bending rigidity of the cord. When the thickness of thecoating layer is too thin, the optical fiber cord tends to become flat,and the bending rigidity required for the optical fiber cord, which is12.74 N·mm² (1.3 kgf·mm²) or more, is not likely to be obtained and thefire retardant property required for the optical fiber cord will not beobtained, either, although a coating material having bending modulus of1,300 MPa or so is used.

On the other hand, when the coating layer is too thick, it becomesdifficult to ensure the loose state of the core wire, which is requiredfor the optical fiber cord. Further, when the bending modulus of thecoating resin is 500 MPa or less, the bending rigidity, which is one ofthe mechanical properties necessary for the optical fiber cord, will beas small as less than 12.74 N·mm², although the thickness of the coatinglayer is made to be 0.30 mm. In this case, when the optical fiber cordis pulled at the right angle (90°) with respect to a connector in astate in which the connector is attached to the optical fiber cord, thebending radius at the connector boot portion may be small, therebyresulting in a possible increase in transmission loss. Due to the reasondescribed above, the bending rigidity required for the optical fibercord is 12.74 N·mm² or more.

In the present invention, the non-halogen fire retardant resin isintended to include resin compositions. Here, being “fire retardant”indicates that the substance has a property which meets the fireretardant property standardized in the horizontal flame test of JIS C3005 as described below. In the present invention, the coating layerformed by the non-halogen fire retardant resin may be designed so as tohave a single layer or a plurality of layers. In the coating layer, atleast the outermost layer thereof (when the coating layer is formed by asingle layer, the single layer itself) is preferably produced by:preparing a resin as a base which contains at least one type of resinselected from the group consisting of a polyamide-series thermoplasticresins, a polyamide elastomer-series thermoplastic resins or a polyesterelastomer-series thermoplastic resins; and blending, to 100 parts bymass of the thermoplastic resin as the base, preferably 18-60 parts bymass, more preferably 25-50 parts by mass, and the most preferably 25-40parts by mass of an ammonium polyphosphate-series fire retardant agent.When the amount of the ammonium polyphosphate-series fire retardantagent is too small, the fire retardant property of the optical fibercord cannot be obtained. On the other hand, when the amount of theammonium polyphosphate-series fire retardant agent is too much, theoptical fiber cord, after being bent for a long period, tends to remainin a bent form, causing a trouble in the line-setting operationthereafter. In addition, the mechanical properties of the coatingmaterial significantly deteriorate in this case.

Examples of the ammonium polyphosphate-series fire retardant agent to beused include the trade name: “Hostaflam” (manufactured by ClariantK.K.); “TERRAJU” (manufactured by Chisso Corporation); and “Sumisafe PM”(manufactured by Sumitomo Chemical Co., Ltd.).

Ammonium polyphosphate itself is soluble to water. However, by employingammonium polyphosphate powder which has been subjected to surfacecoating, this problem of water resistant property can be overcome. As anexample of such a surface-treated ammonium polyphosphate, theaforementioned “TERRAJU” can be mentioned.

When melamine cyanurate, for example, is used as a nitrogen-series fireretardant agent together with ammonium polyphosphate as thephosphorus-series fire retardant, the fire retardant property issignificantly enhanced. Therefore, it is possible to reduce the amountof the phosphorus-series fire retardant agent to be blended. Ammoniumpolyphosphate and the nitrogen-containing compound, as the fireretardant agent, are preferably used together as a mixture of both. Asmelamine cyanurate, “MC”, which is manufactured by Nissan ChemicalIndustries., Ltd, and the like are available.

The phosphorus-series fire retardant agent is supposed to act such thatphosphorus thereof and oxygen react with each other during combustion,thereby forming a film on the surface of the resin and blocking thesupply of oxygen to the resin. In addition, the nitrogen-series fireretardant agent is supposed to act such that it is decomposed at thetime of combustion, thereby generating nitrogen gas and making theatmosphere inactive. In the present invention, it is assumed that thephosphorus-series fire retardant and the nitrogen-series fire retardantact in a multiplicative manner, thereby significantly increasing thefire retardant property.

The total amount of the ammonium polyphosphate-series fire retardantagent and the nitrogen-containing compound-series fire retardant agentis 18-60 parts by mass, more preferably 25-50 parts by mass, and mostpreferably 25-40 parts by mass with respect to 100 parts by mass of thebase resin. When the amount of the fire retardant agent is too small,the satisfactory fire retardant property may not be obtained. When theamount of the fire retardant agent is too much, the optical fiber cord,after being bent, tends to remain in a bent form.

In addition, when the ammonium polyphosphate-series fire retardant agentand the nitrogen-containing compound-series fire retardant agent areused in a mixed state, the ratio of ammonium polyphosphate to the totalamount of ammonium polyphosphate and the nitrogen-containing compound ispreferably at least 50 mass % or more, and more preferably at least 60mass % or more. When the ratio is less than 50 mass %, as the amount ofthe fire retardant agent which is blended into the composition is small,it is necessary to blend the fire retardant agent such that the amountthereof as a whole exceeds the aforementioned 60 parts by mass, in termsof the fire retardant property. As a result, the optical fiber cord,after being held in a bent form for a long period, tends to remain in abent form after being released, thereby potentially causing a trouble tothe line-setting operation thereafter. Further, the mechanicalproperties of the coating material also significantly deteriorate.

It should be noted that, the fire retardant property is enhanced notonly when melamine cyanurate is mixed with ammonium polyphosphate, butalso when other nitrogen-containing compounds such as polyphosphoricacid amide, tris-(2-hydroxyethyl) isocyanate, and melamine are mixedwith ammonium polyphosphate. Further, when these nitrogen-containingcompounds are used in a mixed manner, an effect, which is substantiallythe same as that achieved when melamine cyanurate is mixed, is likely tobe obtained.

In the present invention, as the polyamide-series resin used as the baseresin of the coating material, nylon (polyamide) 12 is preferable interms of the bending modulus property of the material itself. Apolyamide elastomer-series thermoplastic resin is a block copolymerizedelastomer composed of polyamide and polyether. Examples of such apolyamide elastomer-series thermoplastic resin includes “Diamide PAE”(manufactured by DAICEL-HÜLS Ltd.), “Grilon ELX, Griamid ELY”(manufactured by EMS-CHEMIE). Using nylon 12 and the nylon elastomer ina mixed manner does not cause any particular problem.

One example of the polyester elastomer-series thermoplastic resin is ablock copolymerized elastomer formed by polyester and polyether, ofwhich specific examples include “Hytrel” (manufactured by Du Pont-TorayCo., Ltd.), “Pelprene” (manufactured by Toyobo Co., Ltd.) and the like.With respect to the polyester elastomer, a number of products havingdifferent grades of bending modulus are commercially available. Usingthese products of polyester elastomer in a mixed manner does not causeany particular problem.

The bending modulus of the resin which is the base such as nylon 12 andpolyester elastomer is 500-1300 MPa. When the bending modulus of thebase resin is less than 500 MPa, the bending rigidity of the cord of12.74 N·mm² or more cannot be obtained. It should be noted that thebending modulus of the commonly used nylon 12 is 1300 MPa or less.

The higher the elastic modulus of the coating material of the opticalfiber cord is, for example, the more the cord is likely to remain in abent form when the cord is released after being held in for a longperiod a state in which the cord is wound around a bobbin or the like.

When a case in which polyester elastomer is used as the base material iscompared with a case in which nylon 12 is used as the base material,with the same amount of the fire retardant agent blended thereto, orwhen the polyester elastomer-used base material is compared with thenylon-used base material at the substantially the same bending moduluswith respect to the coating material to which the fire retardant agenthas been blended, it is understood, as a result of the study of suchcomparisons, that the polyester elastomer-used base material is lesslikely to remain in a bent form after being released from a bent state.If the base material is in a state to remain in a bent form, theline-setting operation thereafter is more likely to have troubles.Therefore, the polyester elastomer is more preferable as the basematerial in terms of the operation property.

According to the optical fiber cord having the structure of the presentinvention, the mechanical, fire retardant, handling properties requiredfor an optical fiber cord can be enhanced and an optical fiber cordwhich is more reliable can be provided.

The present invention will be described in more detail based on examplesgiven below, but the present invention is not meant to be limited bythese examples.

EXAMPLES Examples 1-12 and Comparative Examples 1-8

An optical fiber having a structure shown in FIG. 1 was produced asfollows such the that thermoplastic resin component and the fireretardant agent were blended according to the blending ratio shown inTable 1 and Table 2 below (the blending ratio is expressed as a relative“parts by mass” value in which the resin component is 100).

A ultraviolet light hardenable resin coating having tensile modulus of1200 MPa was provided on an optical fiber elemental wire whose outerdiameter was 0.25 mm, thereby forming a core wire whose outer diameterwas 0.5 mm. As a tensile strength fiber, three pieces of Kevlar K49 (42mg/m) were used. An optical fiber cord whose outer diameter was 1.1 mmwas produced, and various evaluations were carried out as follows. Theresults are shown in Table 1 and Table 2.

The evaluation method was carried out as follows.

(1) Bending Rigidity

Bending rigidity was measured and evaluated as follows. Accordingly, asshown in FIG. 2, the optical fiber cord 1 of which length was 15 cm wasbent so as to have a bending radius D (=30 mm), the resilient force W(N) which was applied by the bending was measured by a load cell balance8, and the bending rigidity E1 was calculated according to the followingformula (1).Bending Rigidity E 1 (N·mm ²)=0.3483WD ²  (1)

(2) Burning Property

The burning property was determined by: carrying out the horizontalflame test of JIS C 3005 five times; evaluating the case in whichburning was naturally extinguished within 180 seconds for all of thetested optical fiber cords as “◯”; and evaluating the case in whichburning continued more than 180 seconds in at least one of the testedoptical fiber cord as “X”.

(3) 90° Bending Test

The 90° bending test was carried out by: pulling the optical fiber cordat the right angle with respect to an optical connector 9 as shown inFIG. 3 and holding the optical fiber cord in that state for 1 minute atthe load of 5 N; evaluating the case in which the maximum value of theloss increase at the measured wavelength of 1.55 μm was 0.2 dB or lessas “◯”; and evaluating the case in which the maximum value of the lossincrease at the measured wavelength of 1.55 μm exceeded 0.2 dB as “X”.

(4) Remaining of a Bent Form

The degree in which the optical fiber cord remained in a bent form afterbeing released in a bent state described below was determined by:preparing a sample of the optical fiber cord of which length was 25 cm;tightly winding the sample around a mandrel having 14 mm φ five timesand fixing the both ends by a tape; peeling off the tape and pulling outthe mandrel after leaving the sample for 5 minutes in the roomtemperature; leaving the optical fiber cord for 120 minutes; measuringthe curvature radius at the bent portion; evaluating the case in whichthe curvature radius was 40 mm or more as “⊚”; evaluating the sample inwhich the curvature radius was 30 mm or more as “◯”; and evaluating thesample in which the curvature radius was smaller than 30 mm as “X”.

(5) Water Resistance

As the optical fiber cord is used indoors, it is not so important thatthe optical fiber cord is excellent in water resistance. However, incase the optical fiber cord is immersed in water, there is a possibilitythat the appearance of the optical fiber cord differs depending on thewater resistant property thereof. Therefore, the following test wasconducted.

An optical fiber cord was immersed in pure water at 25° C. for 2 hours.The optical fiber cord was then taken out of water, had the cord surfacethereof dried by a dryer, and presence/absence of precipitates on thecord surface was observed. The sample in which any precipitate wasobserved was evaluated as “X”, and The sample in which no precipitatewas observed was evaluated as “◯”.

TABLE 1 Bending Example Example Example Example Example Example ExampleExample Modulus 1 2 3 4 5 6 7 8 Nylon 12 L2140 1100 MPa  100 100Polyamide X4442 500 MPa 100 Elastomer Polyester HTC2751 1280 MPa Elastomer HTC7247 600 MPa 100 100 100 HTC7277 550 MPa 100 100 HTC4767110 MPa HTC4057  60 MPa Ammonium AP422 40 40 15 Poly- AP462 phosphateAP745 25 60 40 AP750 40 TERRAJU 30 30 C60 Melamine MC640 CyanurateProperties Bending 20.58 15.68 16.66 19.60 24.50 12.74 14.70 16.66Rigidity (N · mm²) Burning Test ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ 90° Bending ∘ ∘ ∘ ∘ ∘ ∘∘ ∘ 14φ Bending ∘ ⊚ ⊚ ⊚ ∘ ∘ ∘ ⊚ Tendency Water x x x ∘ x x x xResistance Bending Example Example Example Example Modulus 9 10 11 12Nylon 12 L2140 1100 MPa  Polyamide X4442 500 MPa Elastomer PolyesterHTC2751 1280 MPa  100 80 Elastomer HTC7247 600 MPa HTC7277 550 MPa 100100 HTC4767 20 110 MPa HTC4057  60 MPa Ammonium AP422 15 Poly- AP462 15phosphate AP745 AP750 TERRAJU 15 18 C60 Melamine MC640 10 10 10Cyanurate Properties Bending 18.62 16.66 15.68 15.68 Rigidity (N · mm²)Burning Test ∘ ∘ ∘ ∘ 90° Bending ∘ ∘ ∘ ∘ 14φ Bending ⊚ ⊚ ⊚ ⊚ TendencyWater x ∘ ∘ ∘ Resistance

TABLE 2 Compar- Compar- Compar- Compar- Compar- Compar- Compar- Compar-Bending ative ative ative ative ative ative ative ative Modulus Example1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8Nylon 12 L2140 1100 MPa  100 100 Polyamide X4442 500 MPa 100 ElastomerPolyester HTC2751 1280 MPa  Elastomer HTC7247 600 MPa 100 HTC7277 550MPa 100 100 HTC4767 110 MPa 100 HTC4057  60 MPa Polyolefine EEA  17 MPa100 Ammonium AP422 15 80 15 80 8 Polyphosphate AP462 5 AP745 AP750TERRAJU C60 Melamine MC640 10 13 Cyanurate Metal Kisma 5A 100 150Hydroxide Properties Bending Rigidity 25.48 23.52 12.74 13.72 8.82 6.8613.72 15.68 (N · mm²) Burning Test x ∘ x ∘ x ∘ x x 90° Bending ∘ ∘ ∘ ∘ xx ∘ ∘ 14φ Bending ∘ x ⊚ x ∘ ∘ ∘ ⊚ Tendency Water Resistance x x x x ∘ ∘x ∘

The thermoplastic resin components shown in Tables 1-2 each had thefollowing bending modulus.

Bending Modulus Polyamide: L2140 1,100 MPa   (Nylon 12 manufactured byDAICEL-HÜLS Ltd.) Polyamide Elastomer: X4442 500 MPa (manufactured byDAICEL-HÜLS Ltd.) Polyester Elastomer A: HTC2751 1,300 MPa  (manufactured by Du Pont-Toray Co., Ltd.) Polyester Elastomer B: HTC7247600 MPa (manufactured by Du Pont-Toray Co., Ltd.) Polyester Elastomer C:HTC7277 550 MPa (manufactured by Du Pont-Toray Co., Ltd.) PolyesterElastomer D: HTC4767 110 MPa (manufactured by Du Pont-Toray Co., Ltd.)Polyester Elastomer E: HTC4057  60 MPa (manufactured by Du Pont-TorayCo., Ltd.) Ethylene Ethylacrylate (EEA): A714  17 MPa (manufactured byDu Pont-Mitsui Chemical Corporation)

In addition, the following products were used as the fire retardantagent.

The trade name: “HostaflamAP422” (manufactured by Clariant K.K.) asammonium polyphosphate

The trade name: “HostaflamAP462” (manufactured by Clariant K.K.), thetrade name: “TERRAJU C60” (manufactured by Chisso Corporation) as thesubstance produced by carrying out, to ammonium polyphosphate,surface-coating treatment with a thermosetting resin such as melamine.

The trade name: “HostaflamAP7451”, “HostaflamAP750” (manufactured byClariant K.K.), as ammonium polyphosphate in which “HostaflamAP422” wastreated so as to contain a nitrogen-series compound such astris-(2-hydroxyethyl)-isocyanurate in a manner that the amount of thenitrogen-series compound was less than 50 mass % of the total amount of“HostaflamAP422” and the nitrogen-series compound in a mixed state.

As the nitrogen-series fire retardant, melamine cyanurate of trade name:“MC640” (manufactured by Nissan Chemical Industries., Ltd) was used.

As the metal hydroxide-series fire retardant agent, trade name: “Kisma5A” (manufactured by Kyowa Kagaku Co.) was used.

The following matters are shown by the results of Table 1 and Table 2.

In Examples 1,2 and 3, the optical fiber cord coating whose outerdiameter was 1.1 mm satisfies all of the properties required for anoptical fiber cord as the bending rigidity, burning, 90° bending, anddegree of bending tendency properties. In addition, in the bendingtendency property, when the nylon 12-based sample of example 1 iscompared with the polyester elastomer-based samples of example 2 andexample 3, it is understood that, in a case in which the same fireretardant agent is blended by the same parts, the polyesterelastomer-based samples of example 2 and example 3 are less likely toremain in a bent form after being released from a bent state.

Example 4 and example 12 are the cases in which the product obtained byblending surface-treated ammonium polyphosphate into the base resin wasused. In these cases, satisfactory fire retardant property was obtained,although only 18-30 parts by mass of above-mentioned ammoniumpolyphosphate was blended. In addition, by the results of the waterresistance, it is understood that surface-treated ammonium polyphosphateexhibits excellent water resistance.

Examples 5, 6, 7 and 8 are examples of the cases in which the mixture ofammonium polyphosphate and the nitrogen-containing compound was used asthe fire retardant agent. In these cases, it is understood that theproperties of the optical fiber cord can be satisfied by blending 18-60parts by mass of the mixture.

Examples 9, 10 and 11 are the cases in which the mixture of ammoniumpolyphosphate and melamine cyanurate was used as the fire retardantagent such that the ratio of ammonium polyphosphate to the fireretardant agent mixture of 25 parts by mass was 50 mass % or more. It isunderstood that, when such a composition is used for coating, an opticalfiber cord having excellent properties can be obtained. Among theseexamples, Example 10 is a case in which two types of polyesterelastomers having different elastic modulus from each other were blendedas the base resins. And, it is understood that satisfactory opticalfiber cord properties were obtained in this example. Further, it isunderstood that the optical fiber cords employing surface-treatedammonium polyphosphate such as those of example 10 and 11 exhibitexcellent water resistance.

Comparative example 1 is the case in which a polyamide resin was used asthe base resin and 15 parts by mass of ammonium polyphosphate wasblended. Comparative example 1 is a comparative example of the inventiondefined by claim 2 of the present invention. In Comparative example 1,the fire retardant property, among the properties required for anoptical fiber cord, is not passed.

Comparative example 2 is the case in which a polyamide resin was used asthe base resin and 80 parts by mass of ammonium polyphosphate wasblended. Comparative example 2 is a comparative example of the inventiondefined by claim 2 of the present invention. In Comparative example 2,the resulting optical fiber cord exhibits excellent burning property buttends to remain in a bent form after being released from a bent state.

Comparative examples 3 and 4 are the cases in which polyester elastomerwas used as the base resin of comparative examples 1 and 2. Comparativeexamples 3 and 4 are comparative examples of the invention defined byclaim 2 of the present invention. In Comparative examples 3 and 4, whenthe parts by mass of ammonium polyphosphate which is blended into thecomposition is less than 18 parts by mass, the fire retardant propertyis not satisfactory. When the parts by mass of ammonium polyphosphatewhich is blended into the composition more than 60 parts by mass, theresulting optical fiber cord tends to remain in a bent form after beingreleased from a bent state.

Comparative example 5 is the case in which 100 parts by mass ofpolyester elastomer whose bending modulus was 200 Mpa or less and 100parts by mass of Mg(OH)₂, which is one of the metal hydroxides, wereblended. Comparative example 5 is a comparative example of the inventiondefined by claim 2 or claim 4 of the present invention. In Comparativeexample 5, the resulting optical fiber cord exhibits poor bendingrigidity as well as increase of loss in 90° bending test.

Comparative example 6 employs, as a coating of the optical fiber cord, acomposition in which ethylene ethyl acrylate (EEA), which is one of thepolyolefine resins, was used as the base resin and 150 parts by mass ofMg(OH)₂, which is a metal hydroxide, was blended. Comparative example 6is a comparative example of the invention defined by claim 2 or claim 4of the present invention. In Comparative example 6, in a manner similarto Comparative example 5, the resulting optical fiber cord exhibits poorbending rigidity as well as increase of loss in 90′ bending test.

It should be noted that, in Comparative examples 5 and 6, when the outerdiameter of the optical fiber cord was made to be 1.5 mm by increasingthe resin layer thickness of the outer coating, the bending rigidity ofthe example sufficiently exceeded 12.74 N·mm², thereby eliminating thebending-related problems. Comparative examples 7 and 8 are the cases inwhich the ratio of ammonium polyphosphate to the mixture of ammoniumpolyphosphate and melamine cyanurate was no higher than 50 mass %.Comparative examples 7 and 8 are a comparative example of the inventiondefined by claim 5 of the present invention. In Comparative examples 7and 8, the resulting optical fiber cord exhibited unsatisfactory fireretardant property, although 18 part by mass of the fire retardant agentwas blended.

INDUSTRIAL APPLICABILITY

The optical fiber cord of the present invention is excellent in themechanical, fire retardant and handling properties which are requiredfor an optical fiber cord, and thus preferably used as a highly reliableoptical fiber cord.

Having described our invention as related to the present embodiments, itis our intention that the invention not be limited by any of the detailsof the description, unless otherwise specified, but rather be construedbroadly within its spirit and scope as set out in the accompanyingclaims.

1. An optical fiber cord which is a single core optical fiber cordhaving an outer diameter of 1.2 mm or less, and has a structure in whichan optical fiber core wire having a resin coating is provided at thecenter, a tensile-strength-fiber layer is provided around the outerperiphery of the optical fiber core wire, and a coating layer is furtherprovided around the outer periphery of the tensile-strength-fiber layer,wherein the coating layer is composed of a non-halogen fire-retardantresin, and wherein the coating layer is formed by a composition in which18-60 parts by mass of ammonium polyphosphate is blended with 100 partsby mass of a resin component containing at least one selected from thegroup consisting of polyamide-series thermoplastic resins, polyamideelastomer-series thermoplastic resins and polyester elastomer-seriesthermoplastic resins, and wherein the bending modulus of the resincomponent of the coating layer is 500 to 1,300 MPa.
 2. The optical fibercord as claimed in claim 1, wherein the ammonium polyphosphate is onethat has been surface-treated.
 3. An optical fiber cord which is asingle core optical fiber cord having an outer diameter of 1.2 mm orless, and has a structure in which an optical fiber core wire having aresin coating is provided at the center, a tensile-strength-fiber layeris provided around the outer periphery of the optical fiber core wire,and a coating layer is further provided around the outer periphery ofthe tensile-strength-fiber layer, wherein the coating layer is composedof a non-halogen fire-retardant resin, and wherein the coating layer isformed by a composition in which 18-60 parts by mass of a fireretardant, which consists of ammonium polyphosphate and anitrogen-containing compound, is blended with 100 parts by mass of aresin component containing at least one selected from the groupconsisting of polyamide-series thermoplastic resins, polyamideelastomer-series thermoplastic resins and polyester elastomer-seriesthermoplastic resins, and wherein the bending modulus of the resincomponent of the coating layer is 500 to 1,300 MPa.
 4. The optical fibercord as claimed in claim 3, wherein the ratio of said ammoniumpolyphosphate to the total amount of said ammonium polyphosphate andsaid nitrogen-containing compound is 50 mass % or more.
 5. The opticalfiber cord as claimed in claim 4, wherein said ammonium polyphosphate isone that has been surface-treated.
 6. The optical fiber cord as claimedin claim 3, wherein the nitrogen-containing compound is at least oneselected from the group consisting of melamine cyanurate, polyphosphoricacid amide, tris-(2hydroxyethyl) isocyanate and melamine.